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How does the liver store glucose as glycogen?

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A biochemical flowchart shows the metabolic pathways for carbohydrate utilization, including glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle. The diagram traces the conversion of glucose, fructose, and glycerol through various intermediates, leading to energy production, carbon dioxide release, and biosynthesis of amino acids and porphyrins. Key steps and branches are labeled, with colored boxes highlighting biosynthetic outputs. — Carbohydrate Pathways for the utilization of carbohydrates.

The liver stores glucose as glycogen through a metabolic process known as glycogenesis. This process occurs when blood glucose levels are high, allowing the liver to sequester excess glucose for later use.1

The biochemical pathway involves several key steps:

Glucose Conversion: Once inside the liver, glucose is converted into glucose-6-phosphate, which is then transformed into glucose-1-phosphate by the enzyme phosphoglucomutase.23
Activation: Glucose-1-phosphate reacts with uridine triphosphate (UTP) to form UDP-glucose, an activated form of the sugar.3
Polymerization: The enzyme glycogen synthetase catalyzes the transfer of glucose from UDP-glucose to a growing glycogen chain, increasing the number of glucose units in the polymer.3

While insulin does not directly transport glucose into liver cells, it plays a critical regulatory role by stimulating glycogenesis and inhibiting glycogenolysis (the breakdown of glycogen), thereby promoting the storage of excess carbohydrates.14